Substrate for an implantable microelectrode, electrode element, and electrode system and its manufacturing method
The present disclosure provides a substrate for an implantable microelectrode for being implanted into tissues or brought into contact with a single cell. The substrate comprises a first layer and a second layer deposited on at least a part of a first surface of the first layer. The first layer is based on a first mixture comprising a first photoinitiator and a first component with a first functional group. The second layer is based on a second mixture comprising a second photoinitiator, a second component that is an acid with a second functional group, a base to neutralize the second component, and a third component with third and fourth functional groups. The first and second components are photo-polymerizable, and the third component can cross-link the second component. A swelling capacity of the first layer is smaller than a swelling capacity of the second layer.
1 . A substrate for an implantable microelectrode for being implanted into tissues or for being brought into contact with a single cell, in order to apply or record an electrical signal to or from the tissues or the single cell, comprising:
a first layer; and
a second layer deposited on at least a part of a first surface of the first layer,
wherein each of the first layer and the second layer extends in an x-direction and in a y-direction, and the first layer and the second layer are stacked in a z-direction,
wherein the first layer is based on a first mixture comprising:
(a) a first photoinitiator, and
(b) a first component comprising at least one of a first monomer, a first oligomer, or a first polymer, wherein the first monomer, the first oligomer, or the first polymer comprises a first functional group,
wherein the first functional group is able to be activated by the first photoinitiator, so that the first component is able to be photo-polymerized through the first functional groups, and
wherein the second layer is based on a second mixture comprising:
(c) a second photoinitiator,
(d) a second component comprising a second monomer, a second oligomer, or a second polymer, wherein the second monomer, the second oligomer, or the second polymer is an acid and comprises a second functional group,
wherein the second functional group is able to be activated by the second photoinitiator, so that the second component is able to be photo-polymerized in a linear way through the second functional groups,
(e) a base, wherein the base is able to neutralize the second monomer, the second oligomer, or the second polymer thereby forming a salt, and
(f) a third component comprising at least one of a third oligomer or a third polymer, wherein the third oligomer or the third polymer comprises two functional groups, said two functional groups being a third functional group and a fourth functional group,
wherein each of the third functional group and the fourth functional group is able to be activated by the second photoinitiator, so that the third component is able to cross-link the second component through the third and fourth functional groups,
wherein a swelling capacity of the first layer is smaller than a swelling capacity of the second layer.
2 . The substrate of claim 1 , wherein at least one of the second, third and fourth functional groups is able to form a covalent bond with the first functional group.
3 . The substrate of claim 1 , wherein a ratio of the swelling capacity of the second layer to the swelling capacity of the first layer is 5 or more.
4 . The substrate of claim 1 , wherein the second layer entirely covers the first surface of the first layer.
5 . The substrate of claim 1 , wherein each of the first layer and the second layer has a length in the x-direction and a width in the y-direction, wherein the length of the second layer is shorter than the width of the second layer, and wherein the length of the second layer is shorter than the length of the first layer.
6 . The substrate of claim 5 , wherein the substrate comprises a plurality of the second layers deposited on the first surface of the first layer, wherein the plurality of the second layers is separated from each other in the y-direction.
7 . The substrate of claim 1 , wherein the length of the first layer is longer than the width of the first layer.
8 . The substrate of claim 1 , wherein the first layer comprises a groove formed on the first surface of the first layer or a second surface of the first layer, the second surface being opposite to the first surface in the z-direction, wherein the groove extends in the x-direction.
9 . The substrate of claim 8 , wherein the first layer comprises a plurality of the grooves, wherein the plurality of the grooves is separated from each other in the x-direction.
10 . The substrate of claim 8 , wherein the second layer at least partly penetrates into the groove.
11 . The substrate of claim 8 , wherein the direction of the width of the second layer and the longer direction of the groove are orthogonal to each other.
12 . The substrate of claim 1 , wherein the first monomer, the first oligomer, or the first polymer is a polyurethane or silicone, and wherein the first functional group is an acrylate or methacrylate group.
13 . The substrate of claim 1 , wherein the second component comprises the second monomer and the second monomer is acrylic acid or methacrylic acid, and wherein the second functional group is an acrylate or methacrylate group.
14 . The substrate of claim 1 , wherein the second component comprises a further monomer or a further oligomer, which comprises a fifth functional group, wherein the second functional group and the fifth functional group are able to be activated by the second photoinitiator, so that the second component is able to be photo-polymerized in a linear way through the second and fifth functional groups.
15 . The substrate of claim 14 , wherein the fifth functional group is a methacrylate group, and wherein the further monomer is hydroxyethylmethylacrylate (HEMA).
16 . The substrate of claim 1 , wherein the base comprises NaOH or KOH, and wherein the third oligomer or the third polymer is a polyethylene glycol, and the third functional group is an acrylate or methacrylate group, and the fourth functional group is an acrylate or methacrylate group.
17 . The substrate of claim 14 , wherein the molar ratio of the second monomer, the second oligomer, or the second polymer to the further monomer or the further oligomer is in a range of 1000:1 to 1:1, and wherein the molar ratio of the second monomer, the second oligomer, or the second polymer to the base is in a range of 10:1 to 10:6.
18 . The substrate of claim 1 , wherein the neutralization degree of the acid to the base is 10 to 60%.
19 . The substrate of claim 1 , wherein the molar ratio of the second component to the third component is in a range of 1000:1 to 2:1.
20 . The substrate of claim 1 , wherein the first mixture or the second mixture further comprises a further photoinitiator, a quencher, or a photoabsorber.
21 . The substrate of claim 1 , further comprising a third layer extending from the first layer in the x-direction and in the y-direction, wherein the third layer is integrally formed with the first layer, and wherein the third layer is based on the first mixture.
22 . The substrate of claim 1 , further comprising:
a first electrical conductive layer deposited on a second surface of the first layer, the second surface extending in the x-direction and in the y-direction and being opposite to the first surface in the z-direction,
wherein the second layer, the first layer and the first electrical conductive layer are stacked in the z-direction in this order, and
wherein the substrate is configured to be part of an electrode element for being implantable into a biological sample.
23 . The substrate of claim 22 , wherein the first electrical conductive layer comprises a metal film, a nanoparticle conductor, or a conductive polymer.
24 . The substrate of claim 22 , further comprising:
a third layer extending from the first layer in the x-direction and in the y-direction, wherein the third layer is integrally formed with the first layer, wherein the third layer is based on the first mixture, and
a second electrical conductive layer deposited on the third layer, wherein the second electrical conductive layer is connected to the first electrical conductive layer,
wherein the substrate, the first electrical conductive layer, the third layer, and the second electrical conductive layer form an electrode system.
25 . A method of manufacturing a substrate for an implantable microelectrode, the method comprising:
providing a first mixture comprising a first photoinitiator and a first component, the first component comprising at least one of a first monomer, a first oligomer, or a first polymer, wherein the first monomer, the first oligomer, or the first polymer comprises a first functional group;
forming a first layer by exposing the first mixture to light, wherein the first functional group is activated by the first photoinitiator, causing the first component to photo-polymerize through the first functional groups;
providing a second mixture comprising:
a second photoinitiator,
a second component comprising a second monomer, a second oligomer, or a second polymer, wherein the second monomer, the second oligomer, or the second polymer is an acid and comprises a second functional group,
a base capable of neutralizing the second monomer, the second oligomer, or the second polymer to form a salt, and
a third component comprising at least one of a third oligomer or a third polymer, wherein the third oligomer or the third polymer comprises a third functional group and a fourth functional group;
depositing the second mixture on at least a part of a first surface of the first layer; and
forming a second layer by exposing the second mixture to light, wherein the second, third, and fourth functional groups are activated by the second photoinitiator, causing the second component to photo-polymerize in a linear way through the second functional groups and the third component to cross-link the second component through the third and fourth functional groups;
wherein a swelling capacity of the first layer is smaller than a swelling capacity of the second layer.
26 . The method of claim 25 , wherein forming the first layer includes forming a groove on the first surface of the first layer or a second surface of the first layer, the second surface being opposite to the first surface in the z-direction, wherein the groove extends in the x-direction.
27 . The method of claim 25 , further comprising:
forming a first electrical conductive layer on the second surface of the first layer.
28 . The method of claim 25 , further comprising:
forming a first electrical conductive layer on the second surface of the first layer;
forming a third layer by exposing the first mixture to light; and
forming a second electrical conductive layer on the third layer.
29 . The method of claim 25 , wherein the ratio of the swelling capacity of the second layer to the swelling capacity of the first layer is 10 or more.
30 . The method of claim 25 , wherein the ratio of the swelling capacity of the second layer to the swelling capacity of the first layer is 20 or more.